Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		1 Months Ended
	Dec. 15, 2017	Jan. 31, 2018
Equity [Abstract]
Number of shares issued in public offering	3.2	0.3
Shares issued, price per share	$ 185.00	$ 185.00
Proceeds from public offering of common stock, net of issuance costs	$ 569.8	$ 48.7